Feature: State Machine

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The main goal of this PR is to implement a StateMachineService as described in #25

• based on valtio (vanillla-version)
• Used to create a proxy state object using StateMachineService.create for each chat session (sessions are handled using Grammy's session plugin)
• Changes on the state (or any sub property) can be subscribed using StateMachineService.subscribe or by watching the forwarded event

Other improvements:

• Commands, Services and EventManagers now have a getSingleton (which internal resolves the DI singleton with the tools provided)
• In order to be able to cancel a running process such as answering callouts, we now make use of the native AbortController, this is assigned to a session so that it can be cancelled from anywhere
• Commands now have a new property visibleOnStates to define in which states this command should be visible
• New commands: /help, /debug and /cancel
• Renamed TelegramService to AppService
• Improved documentation
• Cleanups where it just fits

[wpf500]

I obviously don't know the codebase well but from what I can tell it all looks great 😄